1. Field of the Invention
The present invention relates generally to the field of devices for collecting blood samples. More specifically, the present invention discloses a device for safely piercing a plastic segment tube to release a blood sample into a receptacle for subsequent testing.
2. Statement of the Problem
Donated blood is widely used for transfusions to assist patients suffering trauma and during surgery. A soft plastic bag called a blood collection bag is used for gathering blood from the donor. The blood collection bag is connected to a flexible plastic tube and a needle at the distal end of the plastic tube is penetrated into the donor's vein. Blood flows through the needle and tube into the blood collection bag. After the desired quantity of blood has been collected in the blood collection bag, the needle is withdrawn and the tube is heat sealed into a series of segments containing the donor's blood.
Prior to transfusion, each unit of blood must be tested to ensure that it is compatible with the patient's blood type. This is commonly referred to as a "type and cross-match" procedure. In addition, donated blood is often tested for the presence of infectious agents, such as hepatitis viruses and HIV. However, blood samples cannot be obtained directly from the blood collection bag, because of potential contamination of the blood that may occur from contact with a syringe or pipette used to withdraw a sample.
As a result of this problem, the conventional approach has been to heat seal a number of short segments of the plastic tube leading from the donor's arm to the blood collection bag. These sealed tube segments are commonly referred to as segment tubes, pigtails, or segments. The segment tubes are made of soft plastic that can easily bend or buckle. The segment tubes remain attached to the blood collection bag, and are often folded into a group held together with a rubber band. Blood is typically tested shortly after it has been donated, and again immediately before transfusion. In both cases, the laboratory technician simply removes one of the segment tubes attached to the blood collection bag for testing. The customary technique is to use a pair of surgical scissors to cut the segment tube in half at the junction between the sedimented red blood cells and plasma in the blood sample within the segment tube. The section of the segment tube containing the red blood cells is then squeezed to force cells into a test tube for subsequent testing.
This current technique has a number of shortcomings and potential hazards. The segment tube may be under internal pressure, which can cause blood to spray outward when the segment tube is cut. This can expose the technician and work surfaces in the laboratory to potential blood contamination. The scissors also become contaminated with blood, and could cause transmission of blood-borne infectious disease to health care workers, particularly if the technician experiences an injury from sharp edges associated with the scissors. The scissors are often reused without cleaning or sterilization after cutting through a segment tube. This further increases the dissemination of blood-borne microorganisms to work surfaces and drawers where scissors are stored after use. The surface of the donor blood bag can also become contaminated with blood by laying the bag on contaminated work surfaces, or by technicians touching the bag with blood-contaminated gloves or hands. The blood-contaminated blood bag might then contaminate other hospital environments, such as operating rooms and patient areas. Again, this could potentially increase nosocomial and health care worker infection rates from blood contamination (e.g., staphylococcal, streptococcal, hepatitis B and C infections). Finally, failure to clean the scissors between samples could cause subsequent blood samples to be contaminated with trace amounts of blood from preceding samples. This can lead to inaccurate cross-matching, with subsequent safety concerns for patients requiring transfusions. Furthermore, this problem could unnecessarily increase the time and cost for cross-matching and delay transfusion of blood to patients in life-threatening emergencies.
A number of devices have been invented in the past for piercing segment tubes, including the following:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Staebler et al. 5,254,312 Oct. 19, 1993 McMorrow 4,176,451 Dec. 4, 1979 Minase et al. EPO Publ. 0350792 Jan. 17, 1990 ______________________________________
"Introducing the SEG-SAFE.TM. Segment Processor", Alpha Scientific Corp., Southeastern, Pa. (1995)
"Directions for Using SegmentSampler.TM.," Gamma Biologicals, Inc., Houston, Tex. (Nov. 1994).
Staebler et al. disclose a device for collecting a blood sample from a segment tube. The main body of the device has a cup like portion that is inserted into a test tube. The user then inserts a segment tube into the cup like portion of the device and exerts a downward force to enable a piercing element (i.e., a blade or lance) to puncture the segment tube, thereby allowing blood to flow from the segment tube into the test tube. This device is marketed by Innovative Laboratory Acrylics, Inc., of Brighton, Mich., under the name "I.L.A. Safety Segment Slitter."
McMorrow discloses a segment tube cutter with a tapered lower end 8 that is inserted into the test tube 6. A sharp spur 10 cuts the segment tube 11 as it is inserted into the device.
Minase et al. disclose another example of a device for piercing segment tubes. The tubular portion 2 of the device is inserted into a test tube. A cutting edge or needle at the bottom of the tubular portion pierces the segment tube as it is inserted. A hole 7 allows blood to drain from the segment tube into the test tube.
The literature distributed by Alpha Scientific Corp. shows a temporary receptacle for processing segment tubes that includes a needle to puncture the segment tube.
The "SegmentSampler" device marketed by Gamma Biologicals, Inc., is generally similar to that disclosed by Minase et al. However, the lower tubular portion of the device is tapered to accommodate a range of test tube diameters.
The prior art devices fail to address many of the technical and safety issues associated with obtaining a blood sample from a segment tube. An ideal blood sampling device should address the following concerns:
(a) The type and cross-match procedure is commonly performed using any of several different test tubes diameters. It is important that the device be able to accommodate different test tube diameters. In particular, the device should not exert forces on the neck of the test tube as the segment tube is punctured that might cause the test tube to break.
(b) There are no accepted industry standards for the diameter and thickness of the plastic tubing leading to the blood collection bag. Therefore, the device should be able to accommodate different segment tube diameters.
(c) Segment tubes are heat-sealed using at least three different heat-sealing devices that result in different shapes and thicknesses of the heat-sealed ends of segment tubes. In addition, each segment tube has two distinct diameters. The sealed ends have a major dimension larger than the diameter of the body of the segment tube. This further complicates the dimensional variations among the various types of segment tubes. A device with a cylindrical opening to receive the segment tube will tend not to provide a particularly good fit, and may not adequately guide and support the segment tube. The device should be able to accommodate sealed ends having a wide range of dimensions without exerting radial forces on the test tube.
(d) The segment tube should not be allowed to fold or buckle as it is inserted into the device.
(e) The device should not have an opening that restricts insertion of the segment tube to a particular orientation to accommodate the flat sealed end of the segment tube.
(f) The device should minimize contact between the user's fingers and the glass test tube.
(g) The device should prevent contact between the user's fingers and the puncturing element within the device.
(h) After the segment tube has been punctured, the user should not have direct contact with the punctured end of the segment tube to minimize blood splatter and contamination. The device should retain the punctured segment tube so that both can be discarded together.
(i) Considerable downward force may be necessary to puncture the segment tube. The device should provide sufficient structural support to maintain proper orientation for the puncturing element, and to prevent the puncturing element from bending or being dislodged.
(j) If adhesive is used to bond the needle to the device, the adhesive should not be permitted to plug the needle and thereby interfere with drainage of blood from the segment tube through the needle into the test tube.
(k) It is also important to minimize the dispersal of any blood remaining in the device after the segment tube and device have been discarded. Blood tends to remain within the needle and droplets of blood accumulate at the bottom of the device. These droplets of blood can easily become dislodged when the device is discarded and contaminate the surrounding environment.
Thus, the "SegmentSampler" device marketed by Gamma Biologicals, Inc., has a number of shortcomings when compared against the above list of desired features. In particular, the tapered side walls of the SegmentSampler device create radial pressure if used with smaller test tubes (e.g., 10 mm and 12 mm) that can cause the test tube to break when a relatively small downward force is exerted on the device. Also, the SegmentSampler device is not well suited to receive segment tubes having a wide range of diameters and shapes. Wider segment tubes and those with larger sealed ends create an interference fit that can exert radial pressure on the wall of the test tube and break the test tube when the user pushes downward on the segment tube. This device also provides little structural support for the needle. Hence, the segment tube can bend the needle sideways, preventing puncture of the segment tube. The segment tube could also buckle or fold upon itself without being punctured.
The device disclosed by Staebler et al. has many of the same shortcomings. In addition, this device uses a solid lancet to puncture the segment tube that also plugs the opening in the segment tube, and thus interferes with the flow of blood into the test tube. Also, the device requires that the flat end of the segment tube be inserted at a predetermined orientation to allow the lancet to pierce the wall of the segment tube.
3. Solution to the Problem
None of the prior art references uncovered in the search show a device having the structure of the present invention. In particular, the present device has a port for receiving the end of the segment tube that includes a plurality of tapered ribs arranged in a radial pattern with slots interspersed between each adjacent pair of ribs. This configuration allows the device to handle a wide range of segment tube diameters and a wide variance in the dimensions of sealed ends. The medial edges of the ribs create a passageway with a smaller diameter for guiding and supporting the tubular portion of the segment tube so that it does not fold or buckle, thereby enabling the segment tube to present onto the puncturing element. Multiple slots allow the sealed end of the segment tube to be inserted in any orientation. The larger dimensions of the slots allow the larger, sealed end of the segment tube to be inserted without causing folding or bending of the segment tube. The ribs also help to retain the segment tube after it has been punctured so that the device and segment tube can be discarded together.
The segment tube is punctured by the needle above the level of the test tube, and therefore never enters the test tube. As a result, no outward radial forces are exerted on the test tube as the segment tube is inserted into the device.
An annular recess in the bottom of the device accommodates a wide range of test tube diameters without creating radial stresses that might break the test tube. The annular recess contacts only the top rim of the test tube and only a downward force is exerted on the rim of the test tube when a segment tube is inserted into the device. The lower portion of the device housing serves as a protective skirt covering the rim and upper portion of the test tube to protect the user's fingers if the test tube breaks.
In addition, the needle is held firmly in place by a horizontal divider 12, sleeve 18, and a series of lower radial ribs 21 (see FIG. 11). This additional structural support minimizes deflection of the needle when the segment tube is inserted. The lower ribs 17 below the divider 12 increase capillary attraction of blood that may remain at the bottom of the device after the segment tube has been punctured, so that blood droplets are less likely to contaminate the surrounding environment after the test tube is removed and the device is discarded.